Baseball shirts and athletic undershirts are classically made of high bulk materials which absorb perspiration by wicking perspiration away from the body and by encouraging evaporation on the outer surfaces of the shirts. Because of propensity to change in moisture content, the fabric weight, flexibility and temperature factors also change.
The loose-fitting athletic undershirts and baseball shirts which are well known are comfortable, highly usable and wearable and perform adequately.
In spite of the long use of the shirts and the suitability of the shirts, when the shirts are actually used by baseball players the shirts provide several problems. The looseness which provides comfort also provides differential minor obstructions of movement. Changes of weight in the shirt by virtue of water absorption change weight and resistance to arm movements, which the shirt provides.
The flapping of the shirt provides minute unpredictable changes in wind resistance variations and drag on a moving arm. When the moving fingertip speed is greater than 160 feet per second such as in pitching baseballs or softballs, minor changes in the shirt weight, wind resistance or flapping or operation of the shirt may provide slight changes in accuracy or performance. The changes may be augmented by the effects of centrifugal force on the substantial sleeve material of the shirt.
Baseball and softball players have tried to overcome the basic problems by shortening the sleeve lengths. However, such shortened sleeves provide greater climatic variations to arm muscular structures, and again affect control. Players have rolled up or pushed up sleeves, but forces of throwing or pitching work against those shortening efforts.
When throwing, the arm tends to lift the shirt, but the shoulder supports the shirt. Therefore, a loose fitting shirt of the prior art tends to pull out of baseball pants and tends to bunch at the waist, above the belt.
The prior art baseball undershirts have many disadvantages which have been of long standing. Many attempts have been made to overcome those disadvantages, without success.